Upload
bernice-warren
View
233
Download
0
Embed Size (px)
Citation preview
Chapter 28: Protists - structure, function, diversity, evolution, impactProtists (Chapter 28)
1. More structural and functional diversity than any other group of organisms…
2. Most are unicellular, some colonial and multicellular…
3. Most nutritionally diverse eukaryotes
C. mixotrophs – combine photosyn with hetertrophic nutrition
A. photoautotrophsB. heterotrophs
Chapter 28: Protists - structure, function, diversity, evolution, impact
Broken into three general categories based on ecological context:
1. Photosynthetic (plant-like) protists
3. Absorptive (fungus-like) protists
- algae
2. Ingestive (animal-like) protists
- protozoans
Protists
Chapter 28: Protists - structure, function, diversity, evolution, impact
How did such incredible diversity arise?
Protists
Many species resulted from two rounds of endosymbiosis…
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Phylogenetic tree showing the major clades of protists.
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
A complete branch of a phylogenetic tree. Above how many clades are highlighted?
What’s a clade?
Two, the blue and the red because these are complete branches. The green is not complete.
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Euglenozoa Fig. 28.8
Characterized by spiral or crystalline rod within flagella in addition to 9+2 arrangement of microtubules.
Cyrstalline structure has unknown function.
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Euglenozoa Fig. 28.8
Phylum kinetoplastid
- Causes sleeping sickness
- Spread by African tsetse fly- Fatal if untreated
Ex. Genus Trypanosoma
- Evade immune system by repeatedly changing the proteins on the surface of the cell
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Euglenozoa Fig. 28.8
Phylum euglenid
- Found in freshwater
- Photoautotroph if sunlight available otherwise heterotroph by absorbing nutrients from environment (mixotroph)
Ex. Euglena
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Alveolata Fig. 28.8
Characterized by sacs below membrane called alveoli having yet unknown function
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum dinoflagellates
- Abundant as both marine and freshwater phytoplankton
- Bloom (explosion of growth) can cause “red tide”
Kingdom Alveolata
Phytoplankton – phyto = photosynthetic, plankton = “free-drifting”
- free-drifting photosynthetic organisms (cyanobacteria is also a large part of phytoplankton)
- Secrete toxins that bioaccumulate in molluscs making them dangerous to eat
- Have internal “plates” of cellulose giving its characteristic shape…
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Ciliates
- Obviously use cilia to move and feed
- Can have more than one of each
Kingdom Alveolata
Two types of nuclei
- Large (macro) nucleus
- Smaller (micro) nucleus
Ex) Paramecium
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Ciliates
- Arranged in small units each having many duplicates of a single gene
Kingdom Alveolata
Macronucleus
- Contains dozens of copies of genome
- Genes are not on chromosomes (they don’t have chromosome)
- The gene products (i.e. proteins) control daily functions like feeding, waste removal, etc…
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Ciliates
- Food vacuoles fuse with lysosomes
Kingdom Alveolata
Feeding
- Mainly on bacteria, which are moved through oral groove and phagocytosed at “cell mouth” into food vacuoles.
- Undigestable material is egested when lysosomes fuse with cell membrane
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Ciliates
Conjugation
Kingdom Alveolata
Reproduction
- Mostly asexually by “binary fission”
- two organisms exchange haploid micronuclei (see fig 28.12b above and use book for more detail)
- Genetic diversity, NOT REPRODUCTION
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Diatom (Bacillariophytes)
Kingdom Stramenopila
- Unicellular Algae
- Protection from predators
- glass-like silica based cell wall as shown in figure
- Withstand pressures up to 1.4 million kg/m2 (pressure applied by the leg of a table with an elephant standing upon it)
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Diatom (Bacillariophytes)
Kingdom Stramenopila
Reproduction
- Sexual reproduction is not common, but does occur
- Usually asexually by mitosis
- Estimated 100,000 species
Diversity
- Major component of phytoplankton in oceans and lakes
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Golden Algae (chrysophytes)
Kingdom Stramenopila
(chrysos = golden)
- Freshwater and marine plankton
- Contain yellow/brown cartenoid pigments
- All obviously photosynthetic, some species mixotrophs
- Most unicellular, but some, as shown, are colonial
Dinobryon
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Brown Algae (phaeophytes – guess what phaeo means…)
Kingdom Stramenopila
- All are multicellular and most are marine (salt water – ocean)
- Largest and most complex algae (its what you call seaweed)
- Common along temperate costs like ours
Kelp
Chapter 28: Protists - structure, function, diversity, evolution, impact
Phylum Brown Algae
Kingdom Stramenopila
- The body of the seaweed that is plant-like
Thallus Kelp
- Basically, the holdfast, stipe (stem-like) and blades (leaf-like) (see above)
- root-like structure at base solely for anchoring, not absorption like roots of plants
Holdfast
Sea palm (Postelsia)
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylum Brown Algae
Kingdom Stramenopila
This is important to understand because as you might guess, since plants evolved from multicellular algae, they also do this.
Life-cycle: Alternation of Generations
- The two generations are structurally different as opposed to being isomorphic
Heteromorphic
Laminaria (a brown algae)
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians
- Amoeba with threadlike pseudopods
- Amoeba is a general term for a protist that uses pseudopodia to move and feed. There is no one clade or kingdom that consists of amoebas
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians
Foraminiferans (Forams) Radiolarian
- Named for porous shells called tests
- Foramen means “little hole”
- Organic molecules hardened with CaCO3
- Pseudopodia extend through pores of shell and fx in test formation, swimming and feeding
- Pseudopodia called axopodia
- Tests made of silica
Both of these phyla consist of amoebas because…
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans
- Amoeba with lobe shaped rather than threadlike pseudopods belong to this clade:
Now this amoeba belongs to the above kingdom…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans
Phyla: Gymnamoeba
Phagocytosis of a ciliate:
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans
Phyla: Slime Molds (mycetozoans)
Two major types:
Were once thought to be fungus hence the name, but molecular evidence has revealed convergent evolution
1. Plasmodial Slime Molds
2. Cellular Slime Molds
They in part by their life cycles…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans
Phyla: Slime Molds (mycetozoans)
Plasmodial Slime Mold Life Cycle
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans
Phyla: Slime Molds (mycetozoans)
Cellular Slime Mold Life Cycle
Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Rhodophyta
Rhodo = red
Red Algae
Red due to pigment known as phycoerythrin, which masks chlorophyll
Most large and multicellular, living in tropical waters
Alternation of Generations
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Chlorophyta
Chloro = green
Green Algae
Much like plants, systematics has shown close relationship b/w green algae and plants as you would expect…
Two groups
1. Chlorophytes
- More than 7,000 species, most in fresh water- Simplest are unicellular
- These are the ones that live in mutualism with fungus to form lichen
Watermelon snow showing the incredible diversity of chlorophytes
- Chlorophytes and Charophyceans
*Charophyceans and most related to land plants and are discussed at beginning of Ch. 29 with plants
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Chlorophyta
Chloro = green
Green Algae
Larger size and complexity arose via:
1. Colony formation (ex. Volvox) and multicellular filament formation.
2. Repeated division of nuclei without cytoplasmic division (ex. Caulerpa)
3. True multicellular forms with cell division and differentiation (Ex. Ulva)
Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Chlorophyta
Chloro = green
Green Algae
Complicated life cycle of asexual and sexual stages:
Syngamy = fusion of gametes, aka fertilization/conception
Chapter 28: Protists - structure, function, diversity, evolution, impact